The traditional tailgate which closes off the cargo bed of a pick-up truck causes significant aerodynamic drag in its vertical or "closed" position. To reduce drag many users completely remove the tailgate or drive with the tailgate in its horizontal or "open" position. Multiple position tailgates have also been proposed to improve aerodynamic efficiency. See for example:
U.S. Pat. No. 4,585,265 to Mader which teaches a linkage which permits the traditional tailgate to be mounted in a horizontal position over the bed of the cargo area.
U.S. Pat. No. 4,475,759 Wine teaches a pair of brackets to permit remounting of the tailgate in a generally horizontal position between the sides of the pick-up truck cargo area.
U.S. Pat. No. 4,902,066 to Norman teaches a louvered tailgate which improves the aerodynamics of the pick-up truck in comparison to a conventional tailgate.
U.K. Patent specification 459,395 (1937) to Benson Motor Body Company, which teaches a flap which may be hinged at the "bottom" forming a pick-up truck like tailgate, or hinged at the "top" permitting it to lie in a horizontal plane over the bed.